I have been asked to build a deck that is going to have a solarium-type structure erected on it. HO will be doing that part later. He already has concrete piers in place for the deck posts to attach to. They are about 18″ square by 5′ deep. He would like to have tile installed on the part of the deck that will be enclosed by the solarium; so that it will be an extension of the living area of the house. We live in a cold climate(N.Dakota), and he does not intend to heat it. So he will be using it probably spring, summer, and fall.

         Would it be a mistake to tile the floor in such a structure, as I am wondering if there would be any chance of the grout developing cracks. Is it going to be a problem because of the temperature extremes. As far as structural movement, I feel the concrete piers should be stable, as they have been in place for 3 years. One side will attach to the house and the outer end will be supported by a double 2×10 beam. The deck will be 12×24 and the solarium is 12×18. (The outer end being 12′ from the house.)

        My plan is to use 2×10 joists on 16″ centers and probably put 3/4″ plywood or OSB on the part of the floor inside the solarium. If they do go with tile then I would also put down 1/2″ cementboard on top of the 3/4″. Has anyone had experience with a similar situation and what would be things to be careful of?? Is there another option to give them a tile or stone appearance on the floor without the grout issues? Laminate flooring is out because of the possible moisture issues , I think. I would greatly appreciate any good advice! Thanks!

                                                                                          Duey